A woman travels to Spain and falls in love at first sight. They’re married, but he dies of phosphorus poisoning. Back in the US, she remarries, but this husband, too, dies of phosphorus poisoning. The less chivalrous American courts won’t let her off simply for being a woman so it’s up to detective Fleming Stone to uncover the real murderer.
Not one of Wells’s better stories in that it hangs on clues the reader isn’t given until the reveal, but I’d guessed the murderer anyway. Figuring both men had to be killed by the same person, that person would necessarily be Spanish, and there is only one other Spanish character.
Inscription: Leon Leon Knapp on the front flyleaf. How unfortunate that his last name wasn’t also Leon.